Transformer voltage detection in dimmable lighting systems

Abstract

An illumination system detects a peak value of a voltage of a transformer supplying an LED module by analyzing the current value of the voltage and an on-time of the voltage. Based on the detected peak value, a property of the illumination system is adjusted.

What is claimed is: 
     
       1. A method of determining a nominal voltage of a transformer electrically connected to an illumination system comprising a light source and a dimmer, the transformer supplying a voltage waveform having either a first nominal voltage or a second nominal voltage less than the first nominal voltage, each of the first and second nominal voltages falling within different but overlapping voltage ranges, the method comprising:
 determining a peak voltage of the voltage waveform supplied by the transformer to the illumination system; 
 if the peak voltage is less than a minimum voltage of the voltage-range overlap, identifying the nominal voltage of the transformer as the second nominal voltage; 
 if the peak voltage is greater than a maximum voltage of the voltage-range overlap, identifying the nominal voltage of the transformer as the first nominal voltage; and 
 if the peak voltage falls within the voltage-range overlap, identifying the nominal voltage as either the first or second nominal voltage based at least in part on an on time of the voltage waveform supplied by the transformer to the illumination system. 
 
     
     
       2. The method of  claim 1 , further comprising adjusting a property of the illumination system in accordance with the identified nominal voltage. 
     
     
       3. The method of  claim 2 , wherein the adjusted property comprises a current supplied to an LED or a current drawn by a bleeder circuit. 
     
     
       4. The method of  claim 1 , wherein, if the peak voltage falls within the voltage-range overlap, the nominal voltage is determined by at least one of (i) comparing the on time to a predetermined threshold or (ii) comparing a ratio of the on time to the peak voltage to a second predetermined threshold. 
     
     
       5. The method of  claim 4 , wherein the on time is compared to the predetermined threshold, and further comprising:
 if the on time is greater than the predetermined threshold, identifying the nominal voltage of the transformer as the second nominal voltage; and 
 if the on time is less than or equal to the predetermined threshold, identifying the nominal voltage of the transformer as the first nominal voltage. 
 
     
     
       6. The method of  claim 4 , wherein the ratio of the on time to the peak voltage is compared to the second predetermined threshold, and further comprising:
 if the ratio of the on time to the peak voltage is greater than the second predetermined threshold, identifying the nominal voltage of the transformer as the second nominal voltage; and 
 if the ratio of the on time to the peak voltage is less than or equal to the second predetermined threshold, identifying the nominal voltage of the transformer as the first nominal voltage. 
 
     
     
       7. The method of  claim 1 , wherein the transformer is an electronic transformer or a magnetic transformer. 
     
     
       8. The method of  claim 1 , wherein the first nominal voltage is approximately 24 V and the second nominal voltage is approximately 12 V. 
     
     
       9. A method of determining a nominal voltage of a transformer supplying a voltage waveform to an illumination system, the method comprising:
 determining a peak voltage of the voltage waveform supplied by the transformer to the illumination system; 
 determining an on time of the voltage waveform supplied by the transformer to the illumination system; and 
 determining the nominal voltage based at least in part on the on time. 
 
     
     
       10. The method of  claim 9 , wherein the nominal voltage is determined by at least one of (i) comparing the on time to a predetermined threshold or (ii) comparing a ratio of the on time to the peak voltage to a second predetermined threshold. 
     
     
       11. The method of  claim 9 , further comprising adjusting a current supplied to an LED or a current drawn by a bleeder circuit in accordance with the determined nominal voltage. 
     
     
       12. A circuit for determining a nominal voltage of a transformer, the circuit comprising:
 a comparator for (i) determining a peak voltage of a voltage waveform supplied by the transformer and (ii) determining an on time of the voltage waveform; 
 a memory for storing at least one predetermined threshold associated with at least one of on time or a ratio of on time to peak voltage; and 
 an analyzer for determining the nominal voltage of the transformer based at least in part on the on time of the voltage waveform. 
 
     
     
       13. The circuit of  claim 12 , wherein the analyzer determines the nominal voltage of the transformer based in part on the peak voltage of the voltage waveform. 
     
     
       14. The circuit of  claim 12 , wherein the analyzer adjusts a current supplied to an LED or a current drawn by a bleeder circuit in accordance with the determined nominal voltage. 
     
     
       15. An illumination system comprising:
 at least one light source; 
 a transformer for supplying a voltage waveform to the at least one light source; and 
 a circuit comprising:
 a comparator for (i) determining a peak voltage of the voltage waveform and (ii) determining an on time of the voltage waveform; 
 a memory for storing at least one predetermined threshold associated with at least one of on time or a ratio of on time to peak voltage; and 
 an analyzer for determining the nominal voltage of the transformer based at least in part on the on time of the voltage waveform. 
 
 
     
     
       16. The illumination system of  claim 15 , further comprising a dimmer for dimming light emitted by the at least one light source, the dimmer modifying an input to the transformer. 
     
     
       17. The illumination system of  claim 15 , wherein the analyzer adjusts a current supplied to an LED or a current drawn by a bleeder circuit in accordance with the determined nominal voltage.